Rose Diseases: How To Identify And Treat It

How To Identify

The black spot is probably the most common and injurious of all rose diseases. It is characterized by circular black spots, with fringed edges, on the upper surface of leaves. These spots often vary in diameter, running from smaller to fairly larger.

As the infection progresses, many leaves, especially on susceptible cultivars, yellow and drop prematurely. This leaf drop can seriously weaken the plant over time, thereby reducing its general hardiness and flower production. Black spot adores residing in a warm, moist environment. If left untreated, it will heavily damage your rose plants.

How to Treat

The first thing to do to treat black spots is to remove and discard any infected leaves and canes. Watering should be avoided overhead to minimize the amount of moisture on the leaves because this encourages the disease to spread.

Apply a fungicide labeled for black spot control, following the directions of the manufacturer carefully. For organic gardeners, neem oil or a homemade spray of baking soda and water can be an effective treatment. Good air circulation, provided by routine pruning of your roses, can help to inhibit the disease.

How To Identify

The most obvious identifying feature of powdery mildew is a white, powdery coating that appears on the leaves, stems, and buds of the rose plant. Unlike other fungal diseases, powdery mildew likes dry conditions but where the humidity is high.

Leaves may curl and distort, and affected buds may fail to open correctly. If allowed to take hold long-term, the disease will weaken plants, leaving them particularly vulnerable to other roses and garden pests and diseases.

How to Treat

The first step in treating powdery mildew is to remove the diseased portion of the plant. Next, immediately improve air circulation around your roses, either by initially planting at appropriate distances apart or by consistently pruning away crowded and excess growth.

You may spray with a professional powdery mildew fungicide, or go organic with a water-milk-baking soda cocktail. Also, avoid wetting the foliage of your roses; water them from the base instead. This will make it less likely for an outbreak to occur.

How to Identify

Rust is another fungal disease that manifests as small, orange, or rust-colored pustules on the undersides of rose leaves. As the disease progresses, yellow spots may develop on the upper surfaces of the leaves and infected leaves may fall prematurely.

Generally, rust is favored by cool, moist conditions. It is especially conspicuous during spring and fall. Severe infections will weaken the plant and diminish flowering.

Rust Treatment

At the first sign of rust, remove infected foliage and canes and destroy them. Spray with an appropriate fungicide labeled for rust control and continue with timely reapplication rates. Keep an area of clean space around your roses, and remove all debris as the fungus can live in dropped leaves.

Prune your plants adequately to ensure good air circulation. Water your roses in the early day so that foliage dries out before evening.

How To Identify

Gray mold, sometimes referred to as Botrytis blight, is a fungal disease that primarily affects rose buds, flowers, and stem tissue. A gray mold of a fuzzy nature develops on decomposing plant material, and cool and moist conditions advance the disease. 

This can cause buds not to open, and the blossoms could discolor with the characteristic gray mold presence. This disease also encourages cankers to develop on stems and may lead to dieback if left unchecked.

How to Control

Since it is an airborne disease, the best control for botrytis blight is to remove and dispose of bud, flower, and stem parts of the rose that are showing its signs. Keep air moving around the plant by spacing them well apart and snip off dead growth.

Water roses early in the day to allow foliage time to dry. Apply a fungicide that is labeled for botrytis blight, using the product according to the instructions on the label. Consider mulching around the base of the plants to get rid of splashing and inhibit the spread of the disease.

How To Identify

This is a serious fungal disease leaving purplish or dark brown spots on the upper surface of the rose leaf. A white downy growth may develop on the underside. Advance cases yellow and drop leaves early.

Downy mildew thrives under cool, wet conditions especially when humidity is high. If uncontrolled, it could lead to heavy defoliation weakening the plant.

How to Treat

Control down mildew by manually removing and destroying the infected leaves and canes. Allow for good air circulation around the plants through spacing and periodic pruning. Fungicide labeled for the control of downy mildew can be applied, but very carefully following instructions on the label.

Water your roses early in the day, and try not to water overhead to reduce moisture on the leaves. Check your plants for symptoms of the disease regularly. Also, take quick action the very moment you notice the symptoms.

How to Identify

Crown gall is a bacterial disease of rose plants in which large, tumor-like growths, or galls, form on the roots, stems, and crowns. The galls may be large or small and are very often rough and woody.

Over time, they impede the plant's ability to move water and nutrients, leading to such bad effects as stunted growth and yellowing of leaves. Crown gall bacteria enter plants through wounds; therefore, it is also important to handle your roses with care.

How to Treat

Unfortunately, there is no treatment for crown gall once a plant has been infected. The best thing you can do is remove the plant and destroy it to prevent the bacteria from spreading to your other roses.

General Control Measures Avoid injury to plants at planting time, pruning, or cultivation. Use sterile tools around your plants and as with all other rose diseases, consider resistant varieties if crown gall has been a problem in your garden.

How to Identify

Anthracnose is a fungal disease that has small, round spots manifest on rose leaves. Sometimes the color may range from red to purple or brown, and as they enlarge, a light grey center is produced.

Such affected leaves turn yellow and usually fall, causing defoliation. Anthracnose thrives in cool, wet conditions and spreads like a flame if not checked.

How to Treat

Anthracnose can be treated by removing the infected leaves and canes; allowing for improved air circulation around your plants with proper spacing and pruning. Apply a fungicide labeled for anthracnose control.

Be sure to follow all label instructions carefully. In general, water your roses early in the day so the foliage dries. Avoid overhead watering. Monitor your plants regularly for this disease, and take action immediately if symptoms are evident.

How to Identify

Rose mosaic virus is a viral disease that produces many symptoms, which may include yellow or white streaks, lines, or mottling of the leaves. Other symptoms can include stunted growth, a decrease in flowering, and general decline.

 The virus generally spreads through the use of infected plant material, such as grafts or cuttings, and once a plant has the virus, there is no cure for the plant.

How to Treat

There is no treatment for the rose mosaic virus, so prevention is key. Purchase roses only from reputable sources; do not plant infected plant material in your garden. If you suspect a plant has the virus, remove and destroy the plant to prevent its spread to other roses.

Good garden hygiene will also pay off: disinfecting your tools regularly and avoiding unnecessary wounding of your plants.

How To Identify

Rose rosette disease is a viral disease that presents several symptoms that include strange growths, an excess number of thorns, and distorted leaves that are tinged with red. Other symptoms are witches' brooms, which are malformations showing a thick cluster of stunted shoots.

This disease is transmitted by a tiny mite, and when this has occurred to your plants, it cannot be reversed to its former condition. What is treacherous about this disease is that infected rose bushes eventually die.

Treatment

Unfortunately, there is no cure for rose rosette disease; therefore, plants infected with this disease should be immediately removed and destroyed. Generally speaking, regularly inspect your roses for symptoms of this pathogen, and when symptoms are noticed, take appropriate, immediate action to minimize the chance of infection.

Avoid planting roses close together to prevent an environment for the mites that carry the virus to thrive. Resistant plant varieties can be helpful if this has been a persistent problem in the garden

How To Identify

This fungal disease creates small, circular spots in rose foliage. These circular spots are purple, brown, or black and develop a lighter color in the middle of the spot as they increase in size.

Leaves that develop these spots eventually turn yellow and fall off, defoliating the plant. Cercospora leaf spot loves to grow under warm and humid conditions, thus being able to spread quickly without proper treatment.

How to Treat

The treatment for Cercospora leaf spot is the removal and destruction of the infected leaves and canes. Promote air movement around your plants with good plant spacing and pruning as necessary. Apply a fungicide that is labeled for Cercospora control, using care to follow directions on the label.

Water your roses when the day is young enough that drying of foliage will take place and avoid overhead watering. Check on the plants regularly and destroy any showing signs or symptoms of the disease immediately.

How to Identify

Rose canker is identified to have the fungus that forms sunken areas or cankers on the stems of the rose plants. Sometimes, the cankers are colored black, brown, or gray, and very often they induce death back on the affected stems.

The disease generally increases to other plant parts with extended dieback and eventual decline. It is often introduced by more or less deep wounds so the proper handling of your roses is very relevant.

How to Treat

Control rose canker by pruning out and destroying any infected stems, cutting them back to healthy tissue. Also, take the time to sterilize your pruning tool between cuts to help prevent the spread of the disease.

Use a fungicide that is labeled for canker control, taking care to follow all label instructions. Avoid wounding plants any more than necessary, and maintain good garden hygiene through frequent disinfection of your tools.

How to Identify

Sooty mold is a fungal disease, that is distinguished by a black, sootlike coating on the leaves, stems, and buds of rose plants. The mold itself does not cause damage to the plant, but it will block sunlight out and inhibit the plant's photosynthetic capabilities.

Sooty mold often forms on honeydew secretions emitted by sap-sucking insects such as aphids, whiteflies, and scale.

How to Treat

Sooty mold can be treated by first controlling the insects due to which honeydew is formed. Insecticidal soap or horticultural oil can be used for treating aphids, whiteflies, and scales.

Once insects are controlled, sooty mold can be gently washed from the affected parts of the plant. Rose plants that have good air circulation will reduce the chances of sooty mold.

How To Identify

This is a fungal disease that forms areas of discoloration, or cankers-on rose plant stems. The cankered areas can be black, brown, or gray and usually kill the stem back above the canker.

Infection usually progresses to involve other tissues of the plant, causing further dieback and decline. It is usually introduced into a plant through wounds; therefore, it is vital not to injure your roses.

How to Treat

Prune out and destroy affected stems by cutting them back into healthy tissue to control stem canker. Be sure to sterilize your pruning tools between cuts to prevent the spread of the disease.

Apply a fungicide whose label is for canker. Follow the instructions carefully. Avoid unnecessary wounding of your plant. Good garden hygiene, i.e., regular disinfection of your tool, may also help in keeping this infection away.

How To Identify

Phytophthora root rot is a fungal disease causing the rose plant roots to rot and decay. Because of this, infected plants exhibit stunted growth, yellowing of leaves, and wilting. The spores of the disease thrive in pools of water; thus, planting your roses in such areas or poorly drained soils is one way of causing infections.

Once established, it becomes quite difficult to control. In case of serious infections, the result may be the death of the plant.

How to Control

Reduce phytophthora root rot by improving garden drainage through the addition of organic matter to the soil or setting up raised beds. Avoid overwatering your rose plants, watering them in the morning, and allowing the soil time to dry before evening.

More Information Follow fungicide application in Pharos with a product labeled for phytophthora control according to the manufacturer's instructions. If the infection is severe, you will have to cut off and destroy the infected plant to stop the fungus spread to your other roses.

How To Identify

Rose downy mildew is a serious fungal disease causing the formation of purplish or dark-brown specks on the upper side of the leaves. The undersides of the leaves may exhibit a white, downy growth.

Later on, in the disease process, yellowing and premature fall of the leaves can take place. Downy mildew thrives in cool, wet, and especially humid conditions. If not controlled, it will result in a significant loss of leaves with plant weakening.

How to Manage

Remove and discard affected leaves and canes of downy mildew. Plant correctly to allow air circulation around the plants, and prune plants to increase air movement. Apply a fungicide registered for downy mildew control as directed on the label.

For more information see Water Roses early in the day to allow them to dry off before evening and avoid wetting foliage when water. Regularly check your plants for the disease; should you spot some symptoms, take action immediately.

How to Identify

This wilting disease is caused by a soil-borne fungus, which affects the vascular system of rose plants. Yellowing and wilting commence in lower leaves and then progress upwards.

It leads to stunting, leaf drop, and dieback of the portion of the plant. Verticillium wilt is one of the most problematic to control since this disease remains in the soil for several years.

How to Treat

No cure unfortunately for verticillium wilt, this is a big prevention game. Don't plant roses in problem areas from the past and consider planting resistant varieties, if you worry.

If verticillium wilt is truly inconvenient, remove any plant from the garden as soon as you find it, and destroy it to avoid transmitting the fungi to other roses. Practice good hygiene in the garden: frequently disinfect your tools and avoid wounding your plants needlessly.

How to Identify

Rose mosaic is a viral disease exhibiting various symptoms on your plants, showing yellow or white streaks, lines, or mottling on the leaves. Stunted plant growth may also be exhibited with the infected plants along with reduced flowering and an overall decline in the health of a plant.

The virus normally spreads with the help of virus carriers such as grafts or cuttings. It has no chemical treatment once the plant gets the infection.

How to Treat

There is no treatment for rose mosaic disease, so the key is in prevention. Only buy roses from reputable sources and do not place any potentially infected material in your garden.

If you suspect a plant is infected with this virus, remove and destroy it to help prevent the virus from spreading to other roses. Good garden hygiene-like regularly disinfecting your tools and avoiding unnecessary wounding of plants-is also important.

Identifying Characteristics

Rose stem girdler burrows into rose stems, typically leaving distinct girdling scars on infested rose varieties, along with swelling, cracking, and resultant dieback of affected stems. In severe cases, whole plants are affected with resultant stunted growth and reduced flowering.

Rose stem girdlers can be particularly problematic because this pest often remains undetected until damage has reached significant levels.

How to Treat

Control the rose stem girdler by monitoring your plants for damage and removing any injured stems. Insecticidal soap or horticultural oil is effective in its control; apply at the recommended rate on the product label. Physical barriers such as fine mesh or netting also offer protection against the pest.

Good airflow around roses will help decrease the potential for an outbreak.

How to Identify

Rose slugs are the larvae of sawflies that feed on the leaves of rose plants, resulting in a characteristic holing and skeletonizing. The larvae usually come in green or yellowish colors and thus may not easily be seen because of their minute size. A serious attack may result in profound defoliation, weakening the plant to a large extent.

How to Treat

Rose slugs can be controlled by generally inspecting your plants for damage. Remove the damaged leaves and control the pest by using insecticidal soap or horticultural oil. Apply the product according to the manufacturer's directions. 

Sometimes application of a physical barrier such as mesh or netting that prevents pests from reaching your plant is also useful. Good air circulation around your roses will reduce the chance of being infested by the rose slug.

How to Identify

Rose curculio is a small, red-colored beetle in nature that infests the buds and flowers of rose plants. The terminal bud may not open, and flowers are distorted and discolored.

Heavy infestations may stunt the growth and produce fewer flowers on the whole plant. Rose curculio is usually more problematic because it may be undetected until substantial damage has taken place.

How To Treat

Control rose curculio by regular inspection of your plant's damage and removal of the damaged bud or flower. Management of the pest should be made through insecticidal soap or horticultural oil by following instructions provided by the product manufacturer.

Physical barriers like mesh or netting may help in limiting the accessibility of the pest to your plant. Improvement in air circulation within your rose plantations will limit the possibility of an attack by this pest.